Production of allyl alcohol



May 1.1, 1948. A. B. ASH ETAL I PRODUCTION OF ALLYL ALCOHOL 2 Sheets-Sheet 2 Filed June 19, 1945 m my mmc@ E VA E. m mad H .M wmmmfwn Mym E NWW Patented May 11, 1948 Arthur B. Ash, Raymond E. Carlson,y and Nathan Kosln, Wyandotte, and Thomas H. Vaughn, Grosse Ile.Mich., assignors to Wyandotte Chemicals' Corporation, Wyandotte, Mich., a

corporation of 'Michigan Application lJ une 19, 1943, Serial N0.Y"491,488

2 Claims. (Cl. M30-638) 1 The present invention relates to the manufacture of allyl'alcohol. The broad principleV of this invention is essentially based upon the pyrolysis of aliphatic, acylated hydrocarbon compounds in which the radical is split off from the hydrocarbon chaintogether with one hydrogen atom from an adjacent carbon atom, yielding an allyl ester, then hydrolyzing this unsaturated ester. .When a poly-.ester of a saturated aliphatic. compound of the structural formula l erheen-:CH2 le t wherein X and Y represent respectively either an inorganic acid residue or an acyl group, but wherein either X or Y must designate an acyl group, is so pyrolyzed, the acyl radical which is split ofleaves a double bond carbon to carbon linkage atrits point of departure; this results in the production of an unsaturatedvor alkylenic hydrocarbon chain. When the allyl ester is hydrolyzed allyl alcohol is secured. There. is a ley-product formation of lfacetoxy propene-lin many of the operating conditions in the pyrolysis step Where propylene glycol diacetate is treated; and when this is in turn hydrolyzed propionaldehyde results.` Y Y The primary object of the present invention is to efficiently 'and economically produce allylal-V cohol by the hydrolysis of an acyl ester of allyl alcohol. This process is particularly adapted to the production of allyl alcohol from allyl acetate which in turn is secured by pyrolysis of propylene glycol diacetate.

A further object of this invention i-s the provision of a method of hydrolysis of the allyl ester wherein a high percentage yield of -allyl alcohol is secured. More particularly this invention has an object the hydrolysis of the allyl ester by an acid catalyst followed by an alkaline hydrolysis. We have found that the alkaline hydrolysis in tandem relation with the acidic hydrolysis obviates a dicult step of recovery of unreacted allyl acetate. An acid hydrolysis alone can be employed; but there is considerable vunreacted allyl acetate left by this Vmode which lmust rbe separated from the allyl alcohol and reintroduced into a subsequent hydrolyzing step to 'secure a high conversion. Furthermore, from a commercial standpoint, it is necessary to. free the unreactedl allyl ester and propionaldehvde Vfrom the Aallyl alcohol to secure a marketable product. Whereas with a straight aqueous alkaline hydrolysis, the hydrolysis reaction `goes to completion, and Whilethis obviates the step of recovery `of the unreacted ester, the acetic acid present is converted to sodium acetate; it must be reconverted subsequently to acetic acid by a mineral acid. This greatly adds to the cost. The propionaldehyde can be removed most satisfactorily in the acid hydrolysis, as it tends to polymerize'readily in `'alkaline media. v

Our manufacturing process, which is economically and commercially feasible, involves the three essential process steps of (1) esteriflcation, (2) pyrolysis, and (3) hydrolysis.

To the accomplishment of the foregoing and related end, said invention then comprises the features hereinafter fully described and particularly pontedout in the claims', the following description and annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed. It will be understood .that other esters of propylene glycol other than propylene glycol diacetate such, for example, as propylene chloroacetate, propylene glycol dipropionate and propylene glycol dibutyrate may be formed initially, Vpyrolyzed and! hydrolyzed. When `propylene chloroacetate is pyrolyzed, there is formed allyl chloride and 1 chloro-propene 1..., Upon hydrolysis, allyl chlorideis converted to allyl alcohol, for the 1- chloroepropene-l is stable to hydrolysis and is recovered unchanged. It will be appreciated that suitable adjustment of operative conditions in accordance with the known differences vin character of these esters must be made.

In the annexed drawing:

Figure I is a ow sheet illustrating a process for manufacturing allyl alcohol from propylene glycol and acetic acid; e Figure 4II isa Curve showing the relationship of contact times and yields in the pyrolysis step of such process for diierent temperatures and different agents of increased surface area; these said 'agents or materials may be of catalytic nature or may be simply inert.

Figure III is a curve lshowing the relationship of theper cent of'allyl 'acetate hydrolyzed to the Water-ester molal ratio in the acid hydrolysis step of thel process.

'[Nowreferring more particularly to Figure I of ythe drawing, it will be seen thatrpropylene glycol and acetic acid are first introduced to the reaction vessel I where, in the presence of sulphuric acid, they react to form the ester of such polyhydric, saturated alcohol and said acid, i. e., propylene glycol diacetate, in accordance with the :following equation:

HzSOl CHa-CH-CHz -l- 2CHaCOOH OH H Propylene glycol Acetic acid GHz-CH-f-,CHI "l' 2H2O /o 'I /o u C\ CH3 CH3 Prolylene glycol acetate l An excess of acetic acid, over and above the stoichiometric amount theoretically required for reaction with the propylene glycol, is present in the esteriflcation reaction. The yield of propylene glycol diacetic in this first esterification step has been found to be 95% or better of the theoretically obtainable yield.

The reaction mixture Vfrom the reaction vessel l is then conducted to the still 2 where the acetic acid and water are stripped 0E and returned to the acetic acid recovery system (the latter being not shown in Figure I).

The propylene glycol diacetate from the still 2 is then conducted to the pyrolysis tube 3 Where it is subjected to a heat suicient to split off one of the f f radicals, together', with one of the carbon-linked hydrogen atoms of the poly-ester, leaving the mono-ester, allyl acetate, and aceticjacid, as represented by the following equation:

CHa-OH-CHz m CH2=CH-VCH2 -l- CHCOnH O O -O O Aceticacid C\ C\ C\ ons CH3 p y p on.

Propylene glycol diacetate Allyl acetatev There is some Y formation' of l-acetoxy propene-1 which is isomeric with the allylacetate.

The pyrolytic conversion ofthe propylene glycol diacetate occurs in a temperaturerange of 250- 600 C. The amount of yield of the monoester, allyl acetate, is dependent upon the rate of feed of the vaporized Apropylene glycol diacetate through the pyrolysistube, the temperature and the nature of the increased surface area present in the tube. The pyrolysis'will'proceed satisfactorily in an unpacked tubeybut packed tubes containing glass Raschig rings, glass Wool, glass chips, porous plate, calcium chloridal granular charcoal, and the like, have the eiect of increasing the per cent of conversion for any given rate of flow or contact time. The following tables show per cent of conversionv per pass to allylk acetate and l-acetoxy propene-l for varying Irates of flow and temperatures through an unpacked tube and a tube vpacked with glass vRaschig rings respectively. VThe -tube 'emplyed'was' Pyrex glass 17" length by 1" internal diameter. con'- ditioning furnace was used as a preheater to yaporize the propylene glycol diacetate and to'bring said vapors to within` approximately 10.0 C. Vof

the specified reaction 'temperatures Pyrolysis of propylene glycol diacetate through an. unpacked tube as per cent conversion per pass Rate of flow, ml. per min.

1.5 l1"' i/rolyszs of propylene glycol diacetate through a Vtubev pacltdfwz'ths/ Raschzg rings as per cent conversion per pass Rate of flow, ml. per min. Temp.

2 ml. 3 ml. 4 ml. 5 ml. 6 ml.

. Pe;` cent Per cent Per cent Per cent Per cent 500 C 85 19 470 C 48' 25 13 The propylene glycol diacetate may be conducted in the vapor phase direct from the still 2 to the pyrolysis tube, or if condensed after emission from the still 2, it is preliminarily vaporized (viz. heated to above its boiling point of 18S-190 C.) before introduction into the pyrolysis heating zone.

Figure 2 shows Various curves derived from the figures given in the above table.V Thus, it will be seen that the maximum conversion per pass is obtained at 500 C. in a packed pyrolysis tube. By stripping off the pyrolytic products and recycling the unconverted propylene glycol diacetate through the pyrolysis tube 3, the yield of allyl acetate from this step of the process is or better of the theoretical.

'Ihe pyrolyticprodu'cts comprising allyl acetate and acetic acid and some l-acetoxy propene-l are fractionated to remove the aforesaid esters from acetic acid. This requiresan eiiicient fractionating column.

The allyl acetate and l-acetoxy propone-1 recovered from the fractionation column 4 are then introduced to the acid hydrolysis reaction vessel 5, wherein the presence of a mineral acid catalyst, such as aqueous sulfuric acid, they are hydrolyzed to allyl alcohol, propionaldehyde respectively and acetic acid according to the following reactions:

The low boiling propionaldehyde (B. P. 47 C.) is distilled oi from the mixture undergoing hydrolysis as rapidly as itis formed. The aqueous distilland contains allyl alcohol, acetic acid, water and some unhydrolyzed allyl acetate as indicated in the equilibrium reaction equation supra.

The per cent of conversion of the allyl acetate ester to -producefally1f-ualcohol andffabetic acid. is

' illustratedfby :the :curvein'liigurei 3. .-Itwill fthus ever, such amount is preferably'lield lto.a-re1a tively low value of.5%1oz.lesslbyfweiglit1HzSO4 or Aother acid vequivalentionlthe'ibalsis Vvoftotal Water present. f

In the initial` operationo'fr theprocess system, su'cient amountofv anaikali' or inorganidLb-ase,

Vsuch as sodium hydroxide, -is-` -addedtotheacid hydrolysis I reaction vessel lto. neutralizefthe mineral acid catalyst fafter terminatioirof Vv`the-aforesaid acid hydrolysis reaction. While-notessenf tial, nevertheless Y neutralization minimizeslthe reverse reaction of estericaton. 'Inlsubseq-uent operations of the Vprocessfthis neutralization is` accomplished byY a recycling;-procedureyand will be subsequently described. l p' Ihe aforesaid reaction Jmixture 'fromlthe acid hydrolysis reaction vessell5, is then introduced to the fractionating columnf 6V wherethe-allyl alcohol and allyl acetate are--separated 4ofi vfrom the bulk of the acetic-1 acid. The allyl acetate and alcohol come off as constant vboiling mixtures with water at 83 C.-and 88C. respectively.`'1'-he aqueous acetic is left! in the `still and is-educted to the aceticva'cid yrecovery system. I Due'to the relatively smally temperaturev differential 'orff C. between the two constantlboilingzmixturesdescribed above, it would be ia relativelyi-di'icult and expensive procesa-on a commercial scalegrto separate them by fractional distillation. "We have discovered, however, thatV such a separation can be obviated by subjecting theallylalcohoi and allyl acetate mixture (having a slight amount of acetic acid present) .toa Asecond. hydrlyzing treatment in the alkaline hydrolysis reactionfvessel 1, and in which:aninorganicbase, suchas sodium hydroxide, `is Vemployed as'the hydrolyzing agent. A Y

In the alkalinehydrolysis reaction vessel 1, the

allyl acetate, which is l:present is hydrolyzed to,

allyl alcohol and sodium acetate. The slight amount ofacetica'cid present is also neutralized by the sodium hydroxide to form sodium acetate. The allyl alcohol formed in this step supplements the 4quantity formed in the riirsthydrolysis stage. The reaction mixture from fthehydrolysisl vessel 1 is then introduced tothe fractionating coluamn 8 Where-the constant boiling rmixture of allyl alcohol and Water can thenfbe conveniently-separated from the aqueous sodiumacetate. '..The-:sodium acetate isthen returned .to the acid hy drolysis reaction vessel 5 Where'it'is used in place of the original sodium hydroxide,A toA neutralize the mineral alcid catalyst-in theaacidfhydrolysis step. The constant boiling and Water from the iractionating column 8 is then subjected to azeotropic distillation in the still 9 where the allyl alcohol is separated from the water, thus producing the nal product. Entraining agents, such as benzene or methylene chloride may be suitably employed in the azeotropic distillation of the allyl alcohol-water constant boiling mixture. Y

The acetic acid from the acetic acid recovery system is recycled back tothe esterication reacmixture of allyl .alcoholy A.tioncvessei Il. Through A'the -recovery-.of-1aeetic Y l.ac'ld',iitis'therefore.. necessary to add only-alimamount of mineral lacid catalyst present. l"How-fil() Vboxylic Y acids are f suitable.

:ited amou'ntlof virginlacetic acidmto makeup Afor acetic acidunavoidably lost. in :mechanical operations.

` The pyrolysis may beapplied to'esters of, propylene glycol wherein the carboxylgroup or 'groups are.r :attached to either aromatic Vor'the` aliphatic residues. YWe have found that saturated -esters of the various lowermembered valiphaticcar- YWhileV the ester of acetic -acid is preferred, other of thefseriessuch as `propionic, Vn-butyric and hexoic Aloan be used.

- Various ofthe monobasic aromatic acids rcan be used, suchv as ben'zoicy acid. In these cases'these respective carboxylic 'acidsV wouldgbe split fo'` inkstead vof acetic acid. -Suitable acylatingpagents for the polyhydric saturated alcohols, lchlorcihy- Vdrins or'alkylenic oxides arethe carboxylic-acids,

their anhydrides ror'acid halides, such 'as-the chlorides.

cc.V per `minute. Yunder these conditions was about 45%.

The'followng examples serve to explain the principle of our invention to those skilled inA the art and Vmore readily to-enablel themto understand and practice the same:

Example 1 w76 gms. propylene glycol werefed intoia'jrealction chamber connected to a columnpand'condensercontaining 210'g1ms.ofboiling acetic acid.

' 0.3 gm. of concentrated sulphuric acid vwere'dis solved in `the acetic acid. The amount of acetic acid present represented 31/2 `mois'to 1 mol'of propyleneglycol, or a 75% excess of the-stoichi- 'take-oil of the reflux condenser.

K The reaction-mixture' was then distilled, to separate the propylene .glycol diacetate 'from the acetic acid-Water mixture, giving 1.57 gms. of VVpropylene-glycol Adia-cetate. l

This represented 98% of the theoretical yield.

The propylene glycoll diacetate was then passed through a.k preheating `tube heated in the rrange of 35o-400 C., and'thencegpassed through 4an unpacked Pyrex tube (1""by'17") heated to a temperature of 500 C., and at .the rate 'of 23-4 The conversion rate per. pass Under repeatV passes, the 157 gms. of propylene glycol ld-iacetate yielded 73.5 guns. of allyl acetate, or

'757% of the theoretically obtainable yield and 2.45 gms. of 1acetoxyjpropene1. The other components' are unconvertedpropylene,glycol diace- Itate andA acetic acid.

gms. of :the 'isomeric propenyl acetates,

'-fractionally `distilled from the product of .the

foregoing pyrolysis treatment was then added, together with 180 gms; of water (representing 10 toll- #esters molalratio) and 9.,.gm-s. concentrated sulphuric acid,1to a reaction vessel connected -to a fractionating:column1and refluxed.

Propionaldehyde which is formed by hydrolysis of the 1-acetoxy propene-l was continuously removed during the hydrolysis. It weighed 14 gms. The amount of sulphuric acid present represented 5% by Weight on the basis ofthe water present. 14.7 gms..of 50% sodium hydroxide were then added to the distilland to neutralize the sulphuric acid. The mixture was distilled under reflux conditions; no attempt was madeto keep the fractions separated. The allyl acetate-water l column at 47-50 C.

azeotrope mixture boiling at 83 C. distilled voff rapidly, followed by the allyl alcohol-Water constant boiling mixture which boils at 88 C. 'I'he reflux ratio was then progressively-increased until the temperature of 100 C. was attained, leaving a residue of acetic acid and water. This combined distillate after the 4said neutralization Vhad a composition of 15 gms. of allyl acetate, 35

gms. of allyl alcohol and 20 gms. of Water and about 1.5 gms. of acetic acid.

To this mixture 16 gms. of 50% sodium hydroxide was added. This mixture Was then refluxed until the allyl acetate was approximately completely cleaved, which was Within a halfhour. The solution was distilled, and the constant boiling mixture of allyl alcohol-water came off at about Sii-90 C. The amount of allyl alcohol in this distillate was 42.6 gms. Which represents a 98% theoretical yield. The allyl alcohol-Water constant boiling mixture was then dehydrated by azeotropic distillation, yielding 42 gms. of anhydrous allyl alcohol, representing 97% allyl alcohol yield of that theoretically obtainable from the 75 gms. of allyl acetate.

Example 2 The vapors of 174 gms. of propylene oxide were passed into 540 gms. of boiling glacial acetic acid containing 0.92 gm. of concentrated sulphuric acid. The reaction mixture was then distilled to remove .the unreacted acetic acid and water, yielding 458 gms. of propylene glycol diacetate. The so-formed propylene glycol diacetate was then pyrolyzed, as set'out in Example 1 above.

100 gms. of the isomeric propenyl acetates, fractionally distilled from the product of the foregoing pyrolysis treatment was then added, together with 414 gms. of water (representing 23 to 1 H2O-allyl acetate molal ratio), and 20.7 gms. concentrated sulphuric acid, to a reaction vessel connected to a fractionating column set at total reflux and reuxed for one hour until equilibrium was obtained. Propionaldehyde is distilled off from the reaction mixture thru the fractionating 50.7 gms. of 50% sodium hydroxide were then added to the distilland to neutralize the sulphuric acid.

The mixture was fractionated under a 2:1 reux ratio. The fraction coming over between 83 C. and 88 C. contained practically all of the unconverted allyl acetate, a small amount of allyl alcohol and some Water. When the temperature reached 88 C., a constant boiling mixture of allyl alcohol and Water came over. This amounted to 62 gms. and contained\70% allyl alcohol by weight. This was subjected to dehydration by the same mode indicated in Example 1. The fraction which contained the unconverted allyl acetate was returned to the succeeding charge of allyl acetate to be subjected to the acid hydrolysis.

1 Example 3 100 grams of the isomeric propenyl acetates secured as indicated above and 42 gms. of sodium hydroxide in a 20% water solution Were rei-luxed 8 from 1-2 hours to hydrolyze the esters. The propionaldehyde formed is condensed or polymerized in this step by the action of caustic. The allyl alcohol-Water constant boiling mixture was distilled off, leaving aqueous sodium acetate and the polymer in the still pot. Approximately 59 gms. of allyl alcohol-water distillate were obtained, which analyzed 71% allyl alcohol. The allyl alcohol was dehydrated as in Example 1.

Other modes of applying the principle of the invention may be employed, changes being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

We therefore particularly point out and distinctly claim as our invention:

1. In the method of simultaneously making allyl alcohol and propionaldehyde, the steps of pyrolyzing the diacylated ester of propylene glycol to split 0E a carboxylic acid, removing said acid from the pyrolysis reaction products, subjecting the resultant allyl ester and isomeric acyl ester in the presence of each other to an acid hydrolysis to form allyl alcohol, more carboxylic acid and propionaldehyde, respectively, distilling oi the propionaldehyde during such hydrolysis, distilling oi the last-formed carboxylic acid, and then subjecting the resultant allyl alcohol and remaining allyl ester to an alkaline hydrolysis, the several quantities of carboxylic acid produced in the foregoing steps being recovered and recycled to the process as a starting material to form more of the propylene glycol ester.

2. In `the method of simultaneously making allyl alcohol and propionaldehyde, the steps of pyrolyzing propylene glycol diacetate to form allyl acetate, 1acetoxy propene-l, and acetic acid, removing said acetic acid and thereafter hydrolyzing allyl acetate and 1-acetoxy propene-l in the presence of an acid catalyst to form allyl alcohol and propionaldehyde respectively, additional acetic acid also being formed in such hydrolysis, distilling oft' the propionaldehyde during such hydrolysis, distilling off the last-formed acetic acid and then subjecting-the allyl alcohol and remaining allyl acetate to an alkaline hydrolysis.

ARTHUR B. ASH. RAYMOND E. CARLSON. NATHAN KOSLIN. THOMAS H. VAUGHN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Chitwood Aug. 12, 1941 OTHER REFERENCES Number 

